It has been known for some time that the operating efficiency of an internal combustion engine can be improved by altering the size of the flow passage which admits fuel to the mixing chamber of a carburetor, thereby altering the fuel/air ratio. The optimum ratio is, in part, a function of the altitude at which the vehicle engine is being operated. Normally, engine manufacturers supply one jet type for "high" altitude operation and a different jet for "low" altitude operation but, these categories of high and low are rather broad, using, e.g., 6000 feet as a dividing line. Moreover, these categories are too broad in the sense that a change of a few hundred feet of altitude can make a meaningful difference in efficiency of engine operation.
For this reason, certain repair facilities have undertaken to reduce the size of the orifice in the standard jets, the effort being to make a rather small change to suit the engine needs. The manner in which this has been done, however, is relatively crude and involves placing a punch on the jet and manually striking it with a hammer or mallet. As would be expected, this manual technique results in off-center blows and blows which are too hard or not hard enough. Thus, calibration of the hole size is far from being precise, and jets are commonly ruined in a trial and error effort to arrive at the correct size.
Various devices have been developed in the past for adjusting the fuel delivery in an engine, and a number of machines are known for working metal, generally, and particularly for striking to enlarge or chamfer an opening. Examples of this prior art are found in the following U.S. patents:
U.S. Pat. No. 1,367,238, COAKLEY PA1 U.S. Pat. No. 1,531,489, MACREADY ET AL. PA1 U.S. Pat. No. 1,635,945, LEWIS ET AL. PA1 U.S. Pat. No. 1,752,141, BECHE PA1 U.S. Pat. No. 2,455,577, HAGER PA1 U.S. Pat. No. 2,641,941, LUNDEBERG PA1 U.S. Pat. No. 3,150,442, STRAW ET AL. PA1 U.S. Pat. No. 3,641,802, SEGRO PA1 U.S. Pat. No. 3,847,011, ERRETT